To test the hypothesis that in NIDDM, replacement of diets high in saturated fatty acids with diets high in mufa (and low in pufa) will have potentially useful effects on plasma levels of lipoproteins and LDL particle size distribution, susceptibility to oxidative modification of LDL and LDL subfractions, measures of total body lipid peroxidation and monocyte fatty acid composition and ability of monocytes and monocyte-derived macrophages to generate superoxide anion and to oxidize LDL.